// Copyright (c) .NET Foundation. All rights reserved.
// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.

using System;
using System.Diagnostics;
using System.Globalization;
using System.IO;
using System.Net;
using System.Net.Security;
using System.Security.Authentication;
using System.Security.Cryptography.X509Certificates;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Http.Features;
using Microsoft.AspNetCore.Server.Kestrel.Https;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;

namespace SampleApp
{
    public class Startup
    {
        public void Configure(IApplicationBuilder app, ILoggerFactory loggerFactory)
        {
            var logger = loggerFactory.CreateLogger("Default");

            // Add an exception handler that prevents throwing due to large request body size
            app.Use(async (context, next) =>
            {
                // Limit the request body to 1kb
                context.Features.Get<IHttpMaxRequestBodySizeFeature>().MaxRequestBodySize = 1024;

                try
                {
                    await next.Invoke();
                }
                catch (Microsoft.AspNetCore.Http.BadHttpRequestException ex) when (ex.StatusCode == StatusCodes.Status413RequestEntityTooLarge) { }
            });

            app.Run(async context =>
            {
                // Drain the request body
                await context.Request.Body.CopyToAsync(Stream.Null);

                var connectionFeature = context.Connection;
                logger.LogDebug($"Peer: {connectionFeature.RemoteIpAddress?.ToString()}:{connectionFeature.RemotePort}"
                    + $"{Environment.NewLine}"
                    + $"Sock: {connectionFeature.LocalIpAddress?.ToString()}:{connectionFeature.LocalPort}");

                var response = $"hello, world{Environment.NewLine}";
                context.Response.ContentLength = response.Length;
                context.Response.ContentType = "text/plain";
                await context.Response.WriteAsync(response);
            });
        }

        public static Task Main(string[] args)
        {
            TaskScheduler.UnobservedTaskException += (sender, e) =>
            {
                Console.WriteLine("Unobserved exception: {0}", e.Exception);
            };

            var hostBuilder = new HostBuilder()
                .ConfigureWebHost(webHostBuilder =>
                {
                    webHostBuilder
                        .UseKestrel((context, options) =>
                        {
                            if (context.HostingEnvironment.IsDevelopment())
                            {
                                ShowConfig(context.Configuration);
                            }

                            var basePort = context.Configuration.GetValue<int?>("BASE_PORT") ?? 5000;

                            options.ConfigureHttpsDefaults(httpsOptions =>
                            {
                                httpsOptions.SslProtocols = SslProtocols.Tls12;
                            });

                            options.Listen(IPAddress.Loopback, basePort, listenOptions =>
                            {
                                // Uncomment the following to enable Nagle's algorithm for this endpoint.
                                //listenOptions.NoDelay = false;

                                listenOptions.UseConnectionLogging();
                            });

                            options.Listen(IPAddress.Loopback, basePort + 1, listenOptions =>
                            {
                                listenOptions.UseHttps();
                                listenOptions.UseConnectionLogging();
                            });

                            options.ListenLocalhost(basePort + 2, listenOptions =>
                            {
                                // Use default dev cert
                                listenOptions.UseHttps();
                            });

                            options.ListenAnyIP(basePort + 3);

                            options.ListenAnyIP(basePort + 4, listenOptions =>
                            {
                                listenOptions.UseHttps(StoreName.My, "localhost", allowInvalid: true);
                            });

                            options.ListenAnyIP(basePort + 5, listenOptions =>
                            {
                                var localhostCert = CertificateLoader.LoadFromStoreCert("localhost", "My", StoreLocation.CurrentUser, allowInvalid: true);

                                listenOptions.UseHttps((stream, clientHelloInfo, state, cancellationToken) =>
                                {
                                    // Here you would check the name, select an appropriate cert, and provide a fallback or fail for null names.
                                    if (clientHelloInfo.ServerName != null && clientHelloInfo.ServerName != "localhost")
                                    {
                                        throw new AuthenticationException($"The endpoint is not configured for sever name '{clientHelloInfo.ServerName}'.");
                                    }

                                    return new ValueTask<SslServerAuthenticationOptions>(new SslServerAuthenticationOptions
                                    {
                                        ServerCertificate = localhostCert
                                    });
                                }, state: null);
                            });

                            options
                                .Configure()
                                .Endpoint(IPAddress.Loopback, basePort + 6)
                                .LocalhostEndpoint(basePort + 7)
                                .Load();

                            // reloadOnChange: true is the default
                            options
                                .Configure(context.Configuration.GetSection("Kestrel"), reloadOnChange: true)
                                .Endpoint("NamedEndpoint", opt =>
                                {

                                })
                                .Endpoint("NamedHttpsEndpoint", opt =>
                                {
                                    opt.HttpsOptions.SslProtocols = SslProtocols.Tls12;
                                });

                            options.UseSystemd();

                            // The following section should be used to demo sockets
                            //options.ListenUnixSocket("/tmp/kestrel-test.sock");
                        })
                        .UseContentRoot(Directory.GetCurrentDirectory())
                        .UseStartup<Startup>();

                    if (string.Equals(Process.GetCurrentProcess().Id.ToString(CultureInfo.InvariantCulture), Environment.GetEnvironmentVariable("LISTEN_PID")))
                    {
                        // Use libuv if activated by systemd, since that's currently the only transport that supports being passed a socket handle.
#pragma warning disable CS0618
                        webHostBuilder.UseLibuv(options =>
                        {
                            // Uncomment the following line to change the default number of libuv threads for all endpoints.
                            // options.ThreadCount = 4;
                        });
#pragma warning restore CS0618
                    }
                })
                .ConfigureLogging((_, factory) =>
                {
                    factory.SetMinimumLevel(LogLevel.Debug);
                    factory.AddConsole();
                })
                .ConfigureAppConfiguration((hostingContext, config) =>
                {
                    var env = hostingContext.HostingEnvironment;
                    config.AddJsonFile("appsettings.json", optional: true, reloadOnChange: true)
                          .AddJsonFile($"appsettings.{env.EnvironmentName}.json", optional: true, reloadOnChange: true);
                });

            return hostBuilder.Build().RunAsync();
        }

        private static void ShowConfig(IConfiguration config)
        {
            foreach (var pair in config.GetChildren())
            {
                Console.WriteLine($"{pair.Path} - {pair.Value}");
                ShowConfig(pair);
            }
        }
    }
}
